Method of operating an internal combustion engine and motor fuel therefor



United States Patent 3,164,138 METHOD OF OPERATING AN INTERNAL COM- BUSTION ENGINE AND MGTQR FUEL THERE- FOR Robert M. Renter, Fishkill, and George W. Eclrert, Wappingers Falls, N.Y., assignors to Texaco Inc, New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. 21, 1962, Ser. No. 239,370 11 Claims. (Cl. 123--1) The present invention relates to a method for operating an internal combustion engine and, more particularly, to a way to improve the costs of operating gasoline-powered motor vehicles. This invention also relates to a novel fuel composition containing an oil-soluble aluminum soap of an aliphatic carboxylic acid for use in the instant process.

In recent years the motoring public has evidenced a strong demand for more economical means of motor transportation. This has been reflected in the declining sales volume of standard size or large high powered motor vehicles requiring motor fuels or ever increasing octane value. The business judgments of motor fuel refiners recognized this trend by generally abandoning the sale of the so-called superpremium gasolines. During this same particular period there were substantial sales increases of smaller low-powered motor cars including some recently developed economy size domestic cars. The smaller, lighter cars equipped with low horsepower engines not only gave more miles per gallon of gasoline but also operated effectively on lower octane gasolines.

At the present time, the motoring public is showing renewed interest in high performance, more powerful motor vehicles. Not only is a larger proportion of heavier cars being produced but higher horsepower engines are generally being supplied in both large and economy sized cars at this time. While motor car fuel economy is highly desirable, it is recognized that the present trend to high performance cars tends to increase motor fuel costs.

The spark-ignited internal combustion engines in todays cars are designed to operate over a wide range of conditions including high and low speeds, varying load conditions and the like. The carburetor is the principal control device for supplying the fuel in effective fuel-air ratios for the operation of the engine over the various operating conditions. Unfortunately, a carburetor does not deliver the most economical fuel-air mixture for the engine over the full range of operating conditions.

In searching for new ways to improve the economy of operating a car, particular attention has been directed to the fuel itself. It was believed that if the properties of the fuel could be altered in such a way that effective engine operation could be obtained with leaner fuel-air ratios than heretofore employed, then substantial operating economies would be realized. A unique method has now been discovered for achieving improved fuel economy in the operation of a motor vehicle. By this method, the fuel consumption of a gasoline-burning automobile is substantially reduced. A feature of this method is that it is not dependent on the reduction of weight of the vehicle or reduction in the displacement or size of the engine. And, surprisingly, this improvement does not involve any mechanical or hardware change in the carburetor or other parts of a car.

It has now been discovered that car engine operation can be greatly improved by burning in the engine a gasoline having modified fluid properties. More specifically, a more economical engine operation is achieved by burning a gasoline in which the viscosity has been substantially increased. This viscosity increase gives a lower rate of flow of the gasoline through the carburetor under ordinary conditions Without appreciable alteration of the specific volume of air flow through the manifold and results in the delivery to the engine of a leaner combustion mixture having a lower fuel-air ratio with a concomitant increase in fuel economy. Besides increased efficiency, leaner mixture operation results at times in more power and cleaner exhaust if the vehicle was running overly rich.

The discovery that a motor fuel having substantially increased viscosity would be effective in an automobile was surprising. The fact that such a gasoline would improve the fuel economy was most unexpected. While the reasons are not fully understood, it is known that the higher viscosity fuel produces a leaner fuel-air combustion mixture than generally obtained which, despite its leanness, is most efifective under ordinary motoring conditions.

In accordance with this method, a spark-ignited internal combustion engine is operated by burning a motor fuel containing a viscoisty imparting, oil-soluble aluminum soap of a branched chain aliphatic monocarboxylic acid in which the aliphatic radical has from 8 to 30 carbon atoms. The motor fuel of the invention comprises a hydrocarbon mixture in the gasoline boiling range and the aforesaid oil-soluble, aluminum soap of a branched chain aliphatic carboxylic acid in an amount effective to substantially increase the viscosity of the motor fuel over the viscosity of the hydrocarbon mixture. More particularly, the amount of the oil-soluble aluminum soap employed in the motor fuel is effective to increase the viscosity of the motor fuel at least 10 percent up to about 200 percent over the viscosity of the hydrocarbon mixture under the particular conditions selected for the viscosity determinations. The viscosity of the fuel can be measured by any of the standard methods for viscosity evaluations of liquids provided that conditions are selected to minimize dicrepancies which could arise from the evaporation of very volatile components of the gasoline. Viscosities of the gasolines discussed herein were measured by the Kinematic Viscosity procedure (units in centistokes) at 0 F. This temperature of 0 F. was selected arbitrarily for minimizing the evaporation losses during the viscosity evaluation.

The soaps which have been found effective for thickening motor fuels or gasoline are the soaps that are soluble or dispersible in gasoline and comprise the aluminum soaps of aliphatic monocarboxylic acids in which the aliphatic radical is a branched chain aliphatic radical having from 8 to 30 carbon atoms. These aluminum soaps have the general formula:

Al(RCOO) in which R is a branched chain aliphatic radical having from 7 to 29 carbon atoms. The preferred aluminum soaps are those formed from aliphatic monocarboxylic acids in which the branched chain aliphatic radical has from 8 to 16 carbon atoms with the particularly preferred soaps being those within this range in which the branched chain on the aliphatic radical has more than more carbons while soluble in gasoline are essentially ineffective to produce the desired thickened gasoline of the invention. Aluminum stearate, aluminum n-octanoate and aluminum n-hexanoate produced little or no thickening and are ineffective at the low concentrations concerned. Aluminum soaps of branched chain aliphatic monocarboxylic acids in which the alkyl radical has less than 8 carbon atoms were also inefiective because these compounds were not dispersible in gasoline.

As noted above, it is essential that the oil-soluble, aluminum soap of the invention substantially increases the viscosity of the motor fuel over the viscosity of the hydrocarbon mixture or base fuel. A viscosity increase of at least 10% in the motor fuel measured as the Kinematic Viscosity in centistokes at F. is critical to provide a distinct improvement in fuel economy. This critical limit could vary with other procedures for measuring viscosity. Actually, the viscosity of a gasoline containing an oil-soluble viscosity imparting aluminum soap can be increased by several hundred percent or more by adding the above-noted viscosity imp-rovers. However, a viscosity increase in the range of at least to about 200 percent is the critical range to produce the desired operating economies. Viscosity increases from about to 100 percent are preferred with optimum results being realized with viscosity increases in the range of to 100 percent. The foregoing viscosity increases are generally realized by employing an oil-soluble aluminum soap of the invention in an amount from about 0.005 to 0.5 weight percent based on said gasoline with the preferred amounts being between 0.01 to 0.2 weight percent. Excessively high viscosity increases, i.e., substantially over 200 percent, generally produces an unsatisfactory fuel. Excessive viscosity increases in the fuel sufiicient to reduce the fuel/air ratio to less than 0.06 will generally result in misfiring and loss of power.

A base fuel or gasoline containing none of the oilsoluble aluminum soaps of the invention will generally have a Kinematic Viscosity in centistokes of 0 F. in the range of 0.700 to 1.00. Every gasoline of either high or low octane value or high or low volatility can be characterized by a particular Kinematic Viscosity in centistokes at 0 F. readily determinable by known methods. An increase in the viscosity of such a gasoline by at least 10 up to 200 percent by adding an oil-soluble aluminum soap will produce substantial economies in the operation of a spark-ignitedinternal combustion engine.

The motor fuel of the invention is prepared by admixing a suitable amount of the selected oil-soluble aluminum soap directly into the gasoline. A solvent, such as a liquid hydrocarbon or mineral oil, which is compatible with both the aluminum soap and gasoline, may be first used to form a solution of the aluminum soap which can be mixed into the motor fuel or it can be added directly to the gasoline to aid in the solution or dispersion of the aluminum soap. It is understood, of course, that the motor fuel of the invention can also contain the additives conventionally employed in gasoline, such as alkyl lead octane appreciators, alkyl halide lead scavengers, dyes, anti-icing additives, corrosion inhibitors and the like.

As an example of the fuel economies that can be realized by increasing the viscosity of a gasoline according to this invention, it has been observed that a base motor fuel, having a research octane number of 99.4 and a Kinematic Viscosity of 0.928 centistokes at 0 E, which has had its viscosity increased to 1.196 centistokes or about 29%, both the base fuel and the thickened fuel being tested in a standard 1961 automobile engine under 30 rn.p.h. level road conditions showed that the fuel of increased viscosity produced operating economies of 4.5 percent.

Similarly, a premium motor fuel which had had its viscosity increased by 24.6 percent when tested in a General Motors Research engine at 30 mph. level road conditions showed that the fuel/ air ratio was reduced by about 17% and that the fuel economy was improved by about 7.2%.

Gasolines which have had their viscosity increased in t re order of 50 percent according to this invention have shown substantial improvements in fuel economy ranging from 5 to 10 percent or more over the base fuel depending on the load conditions employed. Similarly, gasolines that have had their viscosities increased in the order of 100 percent or more have been observed to provide fuel economies substantially in excess of 20 percent.

The effect of aluminum soaps of fatty acids including the aluminum soaps of both straight chain aliphatic monocarboxylic acids and branched chain aliphatic monocarboxylic acids was determined in this test. The base fuel employed was a premium gasoline having a research octane number of 99.6 and boiling points of P. 1.3.1 and 380 F. El. This base fuel had a Kinematic Viscosity in eentistokes determined at 0 F. of 0.86. The aluminum soaps were added to the base fuel in the indicated percentages by weight and thoroughly blended into the base fuel. The increase in the Kinematic Viscosity in centistokes at 0 F. for the aluminum soaps tested is shown in Table I below:

Fuel economy tests were made in a General Motors Research engine at 30 mph. and 50 mph. level road conditions using aluminum 2-ethylhexanoate in a premium gasoline having a research octane number of 99.5 and boiling points of 88 F. 13.1. and 404 F. El.

Table 11 Fuel Economy in a multicylinder GM Alum. Inc. in engine Soap, wt. Kin. Vise. percent at 0 11,

percent 30 m.p.h. 50 mph.

percent percent Increase Increase Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A method of operating a. spark-ignited internal combustion engine which comprises burning in said engine a motor fuel comprising a hydrocarbon mixture boiling in the gasoline boiling range containing an oil-soluble viscosity improving aluminum soap of a branched chain aliphatic monocarboxylic acid in Which said aliphatic radical has from 8 to 30 carbon atoms in an amount effective to increase the viscosity of said motor fuel measured as Kinematic Viscosity in centistokes at 0 F. by at least 10 percent to 200 percent over the viscosity of said hydrocarbon mixture.

2. A method according to claim 1 in which the Kinematic Viscosity in centistokes at 0 F. of said hydrocarbon mixture is in the range of 0.700 to 1.00.

3. A method of operating a spark-ignited internal combustion engine which comprises burning in said engine a motor fuel comprising a hydrocarbon mixture boiling in the gasoline boiling range containing an oil-soluble viscosity improving aluminum soap of a branched chain aliphatic monocarboxylic acid in which said aliphatic radical has from 8 to 30 carbon atoms in an amount between 0.005 to 0.5 weight percent of said motor fuel and effective to increase the viscosity of said motor fuel measured as Kinematic Viscosity in centistokes at 0 F. by at least percent to 200 percent over the viscosity of said hydrocarbon mixture.

4. A method according to claim 3 in which the viscosity of said motor fuel is increased at least to' 100 percent.

5. A motor fuel composition comprising a hydrocarbon mixture boiling in the gasoline boiling range con taining anorntal aluminum soap of a branched chain aliphatic monocarboxylic acid in which said aliphatic radical has from 8 to 30 carbon atoms in an amount in the range of (1.005 to 0.5 weight percent eifective to increase the viscosity of said motor fuel by at least 10 percent to about 200 percent over the viscosity of said hydrocarbon "mixture.

6. A motor fuel composition comprising a hydrocarbon mixture in the gasoline boiling range containing an aluminum soap of an aliphatic branched chain monocarboxylic acid in which the aliphatic radical has from 8 to carbons and the side chain on said branched chain monocarboxylic acid has at least2 carbon atoms in an amount in the range of 0.01 to 0.2 Weight percent effective to increase the viscosity of said motor fuel by at least 10 percent to about 200 percent over the viscosity of said hydrocarbon mixture.

7. A composition according to claim 6 in which said aliphatic radical has from 8 to 16 carbon atoms.

8. A composition according to claim 6 in which the viscosity of said motor fuel is increased from 20 to 100 percent over the viscosity of said hydrocarbon mixture.

9. A composition according to claim 5 in which said aluminum soap is aluminum Z-ethylhexanoate.

10. A composition according to claim 5 in which said aluminum soap is aluminum isodecanoate.

11. A composition according to claim 6 in which the viscosity of said fuel is increased by to Van Strien et al June 19, 1956 Cardwell et al. Dec. 30, 1958 

1. A METHOD OF OPERATING A SPARK-IGNITED INTERNAL COMBUSTION ENGIN WHICH COMPRISES BURNING IN SAID ENGIN A MOTOR FUEL COMPRISING A HYDROCARBON MIXTURE BOILING IN THE GASOLINE BOILING RANGE CONTAINING AN OIL-SOLUBLE VISCOSITY IMPROVING ALUMINUM SOAP OF A BRANCHED CHAIN ALIPHATIC MONOCARBOXYLIC ACID IN WHICH SAID ALIPHATIC RADICAL HAS FROM 8 TO 30 CARBON ATOMS IN AN AMOUNT EFFECTIVE TO INCREASE THE VISCOSITY OF SAID MOTOR FUEL MEASURED AS KINEMATIC VISCOSITY IN CENTISTLKES AT 0*F. BY AT LEAST 10 PERCENT TO 200 PERCENT OVER THE VISCOSITY OF SAID HYDROCARBON MIXTURE. 